The streaming instability (SI) is currently the leading candidate for triggering planetesimal formation in protoplanetary disks. Recently, a novel variation, the “azimuthal-drift” streaming instability (AdSI), was discovered in disks exhibiting laminar gas accretion. Unlike the classical SI, the AdSI does not require pressure gradients and can concentrate dust even at low abundances. We extend previous simulations of the AdSI to explore the impact of dust abundance, accretion-flow strength, pressure gradients, and grain size. For a dimensionless accretion-flow strength α _M = 0.1 and particle Stokes number St = 0.1, we find the AdSI produces dust filaments for initial dust-to-gas ratios as low as ϵ = 0.01. For ϵ ≳ 1, maximum dust-to-gas ratios of order 100 are attained, which can be expected to undergo gravitational collapse. Furthermore, even in systems dominated by the classical SI, an accretion flow drives filament formation, without which the disk remains in a state of small-scale turbulence. Our results suggest that an underlying accretion flow facilitates dust concentration and may thus promote planetesimal formation.

中文翻译：

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吸积原行星盘中的流不稳定性：参数研究


流不稳定性 （SI） 是目前在原行星盘中触发行星体形成的主要候选者。最近，在表现出层流吸积的盘中发现了一种新的变体，即“方位漂移”流不稳定性 （AdSI）。与传统的 SI 不同，AdSI 不需要压力梯度，即使在低丰度下也可以浓缩灰尘。我们扩展了 AdSI 的先前模拟，以探索尘埃丰度、吸积流强度、压力梯度和晶粒尺寸的影响。对于无量纲吸积流强度_M = 0.1 α粒子斯托克斯数 St = 0.1，我们发现 AdSI 产生初始尘埃与气体比低至 ε = 0.01 的尘丝。当ε ≳ 1 时，最大尘瓦比达到 100 阶，可以预期会发生引力坍缩。此外，即使在以经典 SI 为主的系统中，吸积流也会驱动细丝形成，否则圆盘仍处于小规模湍流状态。我们的结果表明，潜在的吸积流促进了尘埃集中，因此可能促进行星体的形成。